The present invention relates to a device for erasing unnecessary images for reader-printers adapted to project microfilm images on a screen upon enlargement and to copy such images. The reader-printer to which the present invention is applicable has a printer unit of the type designed to project a microfilm image on a photosensitive member in the form of a slit, develop the resulting charge image and transfer the developed image onto paper. The printer unit produces positive copies from either negative films or positive films.
The negative film has a transparent character area of characters, illustrations or the like, an opaque background area and a transparent margin surrounding these areas. Conversely, the positive film is opaque over the character area and the surrounding marginal area and transparent over the background area.
The arrangement for producing positive copies from negative and positive films includes, for example, a charger changeable to positive or negative polarity, a photosensitive member chargeable to positive or negative polarity, and a developing unit adapted for normal development or reversal development selectively by changing the developing bias. When this arrangement is used for negative films, the light passing through the transparent area of the film is projected on the photosensitive member, and toner is deposited on the portion of the member exposed to the light. In the case of positive films, on the other hand, the portion of the photosensitive member left unexposed to light is developed. Reader-Printer RP505 manufactured by Minolta Camera Kabushiki Kaisha comprises such an arrangement.
When a positive copy is to be obtained from a negative film (hereinafter referred to as "N.fwdarw.P case"), as well as when a positive copy is to be prepared from a positive film (hereinafter referred to as "P.fwdarw.P case"), the surrounding margin will be developed if printed as it is. However, the developed margin is unnecessary for the user, and the absence of the margin is rather preferable.
On the other hand, it may be desired to copy a specific area only of the image on a film. For example, there arises a need to copy a specific portion only of the customers list used in banks, etc. and recorded in COM (computer output microfiche) in which data as to a large number of customers is listed up in each frame. When conventional reader-printers are used in such a case, the image within the entire frame is copied, so that it is practice to cut off the necessary portion only from the copy and affix the copy portion to paper of suitable size.